Echinacea Side Effect: Gut Changes

Dec. 20, 2006 - The popular herb echinacea has a side effect: It changes the balance of gut bacteria, a small study shows.

Whether this is good or bad isn't yet known.

One of the bacteria that seem to increase, bacteroides, has been linked in other studies to diarrhea, inflammatory bowel disease, and coloncancer, researchers report. But there's no direct evidence that echinacea causes or worsens any of these diseases, says study researcher Jerald C. Foote, PhD, RD, of the University of Arkansas in Fayetteville.

"We don't know this is caused by echinacea for sure," Foote tells WebMD. "We are not claiming that echinacea will cause things like that. But if you are taking echinacea and have a history of gastrointestinal problems, maybe you need to take a further look at it."

The study does not impress echinacea researcher Bruce P. Barrett, MD, PhD, of the University of Wisconsin in Madison. Barrett is a member of the scientific advisory board of the American Botanical Council, a non-profit educational group, and the leader of a 2002 clinical trial that found echinacea to have no effect in treating the common cold.

"The low number of subjects, lack of control group, and irrelevant outcome measure detracts from scientific value [of this study]," Barrett tells WebMD in an email. "[The] implied relevance to actual human disease is speculative at best."

Naturopathic doctor Jean-Jacques Dugoua, ND, a researcher at Toronto's Hospital for Sick Children, studies echinacea and other supplements. Dugoua finds the Foote study very interesting -- but notes that bacteroides are normal gut bacteria that can protect against more dangerous bacteria.

"This study suggests that perhaps echinacea plays around with the gut-floor bacteria more than we thought it did," Dugoua tells WebMD. "Maybe that is a good thing, and maybe it is a bad thing. But we did find echinacea to be well tolerated in our safety studies."

Echinacea Side Effect?

Foote, a dietitian, says he began the small study after people taking echinacea asked him whether the herbal remedy might be causing their diarrhea. A review of the scientific literature revealed no information on the effect of herbal supplements on the gut.